/* ----------------------------------------------------------------------  
* Copyright (C) 2010 ARM Limited. All rights reserved.  
*  
* $Date:        29. November 2010  
* $Revision: 	V1.0.3  
*  
* Project: 	    CMSIS DSP Library  
* Title:        arm_fir_init_q15.c  
*  
* Description:  Q15 FIR filter initialization function.  
*  
* Target Processor: Cortex-M4/Cortex-M3
*  
* Version 1.0.3 2010/11/29 
*    Re-organized the CMSIS folders and updated documentation.  
*   
* Version 1.0.2 2010/11/11  
*    Documentation updated.   
*  
* Version 1.0.1 2010/10/05   
*    Production release and review comments incorporated.  
*  
* Version 1.0.0 2010/09/20   
*    Production release and review comments incorporated.  
*  
* Version 0.0.5  2010/04/26   
* 	 incorporated review comments and updated with latest CMSIS layer  
*  
* Version 0.0.3  2010/03/10   
*    Initial version  
* ------------------------------------------------------------------- */ 
 
#include "arm_math.h" 
 
/**  
 * @ingroup groupFilters  
 */ 
 
/**  
 * @addtogroup FIR  
 * @{  
 */ 
 
/**  
 * @param[in,out]  *S points to an instance of the Q15 FIR filter structure.  
 * @param[in] 	   numTaps  Number of filter coefficients in the filter. Must be even and greater than or equal to 4.  
 * @param[in]      *pCoeffs points to the filter coefficients buffer.  
 * @param[in]      *pState points to the state buffer.  
 * @param[in]      blockSize is number of samples processed per call.  
 * @return The function returns ARM_MATH_SUCCESS if initialization is successful or ARM_MATH_ARGUMENT_ERROR if  
 * <code>numTaps</code> is not greater than or equal to 4 and even.  
 *  
 * <b>Description:</b>  
 * \par  
 * <code>pCoeffs</code> points to the array of filter coefficients stored in time reversed order:  
 * <pre>  
 *    {b[numTaps-1], b[numTaps-2], b[N-2], ..., b[1], b[0]}  
 * </pre>  
 * Note that <code>numTaps</code> must be even and greater than or equal to 4.  
 * To implement an odd length filter simply increase <code>numTaps</code> by 1 and set the last coefficient to zero.  
 * For example, to implement a filter with <code>numTaps=3</code> and coefficients  
 * <pre>  
 *     {0.3, -0.8, 0.3}  
 * </pre>  
 * set <code>numTaps=4</code> and use the coefficients:  
 * <pre>  
 *     {0.3, -0.8, 0.3, 0}.  
 * </pre>  
 * Similarly, to implement a two point filter  
 * <pre>  
 *     {0.3, -0.3}  
 * </pre>  
 * set <code>numTaps=4</code> and use the coefficients:  
 * <pre>  
 *     {0.3, -0.3, 0, 0}.  
 * </pre>  
 * \par  
 * <code>pState</code> points to the array of state variables.  
 * <code>pState</code> is of length <code>numTaps+blockSize-1</code>, where <code>blockSize</code> is the number of input samples processed by each call to <code>arm_fir_q15()</code>.  
 */ 
 
arm_status arm_fir_init_q15( 
  arm_fir_instance_q15 * S, 
  uint16_t numTaps, 
  q15_t * pCoeffs, 
  q15_t * pState, 
  uint32_t blockSize) 
{ 
  arm_status status; 
 
  /* The Number of filter coefficients in the filter must be even and at least 4 */ 
  if((numTaps < 4u) || (numTaps & 0x1u)) 
  { 
    status = ARM_MATH_ARGUMENT_ERROR; 
  } 
  else 
  { 
    /* Assign filter taps */ 
    S->numTaps = numTaps; 
 
    /* Assign coefficient pointer */ 
    S->pCoeffs = pCoeffs; 
 
    /* Clear the state buffer.  The size is always (blockSize + numTaps - 1) */ 
    memset(pState, 0, (numTaps + (blockSize - 1u)) * sizeof(q15_t)); 
 
    /* Assign state pointer */ 
    S->pState = pState; 
 
    status = ARM_MATH_SUCCESS; 
  } 
 
  return (status); 
} 
 
/**  
 * @} end of FIR group  
 */ 
